Tire retreading mold



Jan. 18,1944. R a HAWKNSQN 2,339,696

TIRE RETREADING MOLD Filed Aug. 10, 1942 l 2 Sheets-Sheet l 2Sheets-Sheet 2 P. E. HAWKINSON TIRE RETREADING MOLD Filed Aug. .10, 1942Jan. 18, 1944.

S ATE.

1 'vices. combinations of devices of parts hereinafter described anddefined in the I Patented JdnJlBQlO sf AT'auT..-";orsios I 'rn't r:mamas MOLD v PauiE. Hawkinson, Minneapolis, ltiinn.,-assignor PaulE."Hawkinson Company. Minnea Minn, a corporationot MinnesotaApplicationiA 10, 1942 Se NOJMJ: v I if My present invention provides animproved mold for use in the retreading of pneumatic tires; and,generally stated. consists oi the novel deand arrangement Particularly,this invention is an improvement p or Patents molds The'diametri'callyopposite'sides of these molds are parallel so that the mold may be saidto be cylindrical.

the so-called matrix or mold disclosed in my 7 Nos. 1,917,261 and1,917,262. Such. are extensively used in connection with-- thecommercially well-known Hawkinson Sys tern" of retreadin'g pneumatictires and are vflator substantially flat in transverse cross section.

5 01am. (on. 18-18) y 4 in use amen indicate like mic-imam:

r theseveral views.

V casingis indicated by dotted lines by the charac tenA. The matrix orcuring ring, indicated by Ashithe'rto generally constructed, the matrixhas been made from sheet steel strips .crimped cross-sectionally to formcircumferentially extended sealing, ribs,'and sometimes also treaddeforming ribs; and theendsoffthe, matrix 1 'iorming sheet were thenunited by welding or brazing. Matrixes or molds thus made would. I

under expanding pressure of a tire placed therein and inflated, tend tospread, laterally and'expand circumferentially and, moreover, the weldedor brazed Joints were frequently not as strong as v i the main body ofthe matrix.

My present invention overcomes the above deiects and produces astronger. safer, more eiflcient. and better appearing mold. Theinvention involves not only the improved mold or article, but animproved process of producing the same. In this specification the termswelding or brazing are used synonymously.

In the description of this improved device, the mold," is described asmade up of two-important elements, to wit: the matrix or curing ring anda reinforcing band. p

In accordance with my invention 1 first make the matrix or curing ringfrom a ribbon-like metal strip, by bending the same into cylindricalform and rigidly connecting the abutting ends thereof by weldin The moldis then completed by making a reinforcing band out of a ribbonlike sheetor strip of metal, preferably steel, which is then placed around thematrix and set with the joint at its abutting ends circumferentiallyoffset from the welded joint of the abutting ends of the matrix. Thejoint formed by the abutting ends or the reinforcing band should be setdiametrically opposite the joint of the matrix.

A commercial form of the improved device is illustrated in theaccompanying drawings where- Piss. 4 and Referring. to the drawings:

Fig. 1 is a plan view or the mold;

"Fig. 2 is a side elevation of the mold shown in and and lower portionsofthemold.

In Fig. 8 the cross-section or a pneumatic tire numeral. I'll. isfmadeof sheet metal, preferably sheet steel, and is bent into cylindrical.iorm I with it ends abutting at II. This curing ring,

' at or near its edges, is crimped or corrugated toformlendless sealingribs 12 and also interme- "diate tread designvforming ribs l3. Thesealing ribs II, in this preferred arrangement, have out- 1 turnedflanges I2.

' Placed around and closely engaging the extenor, of the curing ring 10is a reiniorcing band ll, preferably also of sheet steel, bent intocylindrical 10m and havins its abutting ends united at 15. The extremeedges of the reinforcing band II .are crimped or bent at ll to embrace,the edge flanges I! or the matrix or sealing ring II. The means forapplying heat to the mold is applied around the exterior or thereinforcing band I. The means for this purpose,

illustrated in the drawings, is a coiled steam pipe i6 preferably weldedto the exterior thereof.

The preferredmethod or manner of produc ingthis mold is as follows:First, the matrix or 1 V curing ring I0 is produced and its abuttingends I l are united by welding produced either electrically or by anacetylene torch, the latter operation being the one that I have employedin practice. This welding. will frequently produce a roughness on theinterior and exterior of the curing ring which should be ground oilbefore the reinforcing band is applied. When the ends are thus weldedthe curing ring becomes an annular sheet metal structure.

As the next step the clamping band 14 will be produced of a diameterwhich will tightly flt around the endless annular curing ring or matrix.a

In the initial application of the clamping band around the curing ring,the flanges l4 may be turned inward at right angles with the cross-sec ss-seemed a transverse section tahen on the line V I 3-3 of Fig.1,showing the parts on a larger scale; 7

5 are irasmentary on the same' scale taken in section-on-the line 4-4 orFig. 1 and showing, respectively, upper oi the'retreed.

" tube It wiu welded Joints. l

the mold.

tion thereof. Prei'ercbiy, the clunpin: bend is madeoi' such lenzth thatwhen Placed in close. but not the closest possible contact with thecuringring,therewillbeespeceeboutfioisninch between the abutting ends ofsaid clamping band. Next, by tightly drawing a cable or chninaround theclamping band, it is contracted into very tlrht and close engagementwith the said curing ring and while under such compressing strain, theheat is applied to the Joint II and'as the molten metal is insertedbetween the shutting endsoi' said Joint ll, there will be an expansionor the with the curing rinI.

the flanges it can be clinched or turned inward, l

as shown in Fig. 3, thereby uniting the curing ring and reinforcinghendinto the most intimate kind Y of connectionulnd Preventing thecuring ring from being expanded, either redislly orleterally,

under pressure As a last operation the heating-means or coiled beapplied around and rigidly secured to the clamping bind; it is, oicourse, hishly' imponmt that the In the preferred and shove described ar-rangeis straight or, otherwise stnted,- the clamping band has parallelsides [and What-'I-clnimis:- I" 1. A tireretreeding' mold comprising anendlesa annular sheet metal ring, an endless producedv thereon inthecuring sign-iorminz welded or hient of the mold, the clamping band; intrans- 'verse cross-section;

'8. The etructure'deiined the heating menus in in in claimri, in whichthe nature of a steam- J conducting coiispplied around the exterior ofthe clampinghand in direct heat-conducting contact therewith,

4; The structure defined in claim 1, which metrically opposite in: rinz.r

' "PAUL E.

